Hydraulic dredge



March 18, 1958 R. T. HOFFMAN 2,826,836

HYDRAULIC DREDGE I 2 Sheets-Sheet 1 Filed Feb. 12, 1949 IITTU EY March 18, 1958 R. T. HOFFMAN 2,826,836

HYDRAULIC? DREDGE 2 Sheets-Sheet 2 fglfliVENToR. 4M

Filed Feb. 12, 1949 nited States This invention relates to a hydraulic dredge that is particularly useful where the formation of gases in the dredge liquid within the suction pipe hinders the dredging operation. Reference is made to my application Serial No. 773,565, dated September 12, 1947.

With the present invention this hindrance to the dredging operation is obviated and the dredging operation is further facilitated.

' The invention may be understood from the description in connection with the accompanying drawing, in which: Fig. l is a side view showing an embodiment of the invention;

liig. 2 is a plan view of a part of Fig. 1 on an enlarged sca c;

Fig. 3 is a section along the line 33 of Fig. 2;

Fig. 4 is a section along the line 44 of Fig. 3;

Fig. 5 is a sectional plan view of another part of Fig. 1 on an enlarged scale;

Fig. 6 is a section at a right angle to Fig. 5;

Fig. 7 is a sectional plan view of another part of Fig. l on an enlarged scale;

Fig. 8 is a section along the line 8-8 of Fig. 7; and

Fig. 9 is a vertical section showing a modification.

In the drawings, reference character 1 indicates a rotary type of dredge pump which may be installed in a dredge. The impeller of this pump, not shown, is driven by a shaft 2 from any convenient source of power; the discharge pipe, not shown, may :be in any direction perpendicular to the shaft 2. A fixed suction pipe 3 connects the suction side of the dredge pump 1 through the hull 4 of the dredge to a movable suction pipe 5, which is adapted in one of several usual ways to rotate about its upper end, while maintaining the integrity of the suction system, in order to reach the material to be dredged. This suction pipe 5 is supported by mechanical means not shown for raising and lowering it. It may he strengthened by additional structure not shown. The means provided for rotation are represented by a ball joint 6, though such means usually allow motion of the movable suction pipe 5 in the surface of a single plane or cone which is fixed with relation to the suction pipe 3 and the rest of the structure of the dredge. The movable suction pipe 5 may have its rigidity interrupted by a ball joint 7 shown dotted since it is usable but not necessary. A cutter shaft (not shown) may extend to the lower end of the pipe 5 in order to operate a cutter head (not shown) for mechanically loosening material on the bottom. The lower end of the movable suction pipe 5 is not shown, since it may consist of a variety of usual and unusual structures. The usual flanges in the suction pipes 3 and 5 are not shown in the drawing.

An ejector 8, representing any of the known types of vacuum pump, is operated :by a fluid under pressure through a pipe 9, which is controlled by an inlet valve 10 which is of a diaphragm operated type. An outlet pipe 11 is provided for the ejector 8. A suction pipe 12 extends from the ejector 8 to a gas accumulator chamber 13.which is connected to the suction pipe 3. A cutoff valve 14 and a diaphragm operated throttle valve 15 are provided in the suction pipe 12. The accumulator chamber 13 is connected to the suction pipe 3 at a location along the length of pipe 3 as near as practicable to the cross-section where the minimum internal pressure exists while dredging. This chamber 13 is so located as to include the lowest pressure area in the cross-section at which it is connected. If more than one location of minimum internal pressure exists in the fixed suction pipe atent-O 2,826,836 Patented Mar. 18, 1958 ice 2' 3 while dredging,leither' simultaneously or at diflerentf times, additional accumulator chambers 13 not shown, may be installed either with'or'iwithout the appendages shown. v

A float chamber 16 of standard manufacture contain-' ing a float not shown, is provided. The effective crosssectional area of this float chamber is reduced, if necessary. The controlling force from this float may be either of the throttling type orof the snap acting type. An example of this type of mechanism is shown and described in United States Patent No. 2,356,970; such devices are sold by the Fisher Governor Company of Marshalltown, Iowa and known as Displacement Type Level-Trol, Type 2405- 248. This controlling force is conveyed by a pipe 17 to a three-way valve 18. The operator may by setting this valve, choose to send the controlling force either to. the diaphragm of the valve 10 through a pipe 19 or to the diaphragm of the valve 15 through a pipe 19'.

The upper portion of the float chamber 16 is connected to the gas accumulator chamber 13, through a pipe 20, a strainer 21, and a cutoff valve 22. The lower portion of the float chamber 16 is connected to a Water pipe 23 for introducing flushing water, with a control valve. 23". The lower portion of this float chamber is also connected to the accumulator chamber 13 through a check valve 24 and a cut off valve 25. The necessary fittings and unions for assembly are not shown. The check valve 24 permits liquid to flow from the pipe 23 into the accumulator chamber 13, but not in the reverse direction. The water pipe 23 may be connected to any point from the check valve 24 through the float chamber 16 to and including pipe 20, as long as the flow of water from the pipe 23 normally passes through the check valve 24.

In operation, water flows from the pipe 23 into the accumulator chamber 13. Gases which collect in this chamber 13 from the dredge liquid are removed by the ejector 8 in order to prevent gases from interfering with the normal operation of the dredge pump 1. When insufficient gases collect to satisfy the requirements of the ejector 8 under the then existing conditions, dredged liquid rises in the accumulator chamber 13. When the level of the dredge liquid rises above the water level in the float chamber 16 or its connecting piping, the check valve 24 closes, preventing dredged liquid or other matter from moving toward the float chamber 16, and simultaneously causing the water that is being discharged from the .pipe 23 to raise the water level in the float chamber 16 and actuate the float therein.

When the three way valve 18 is positioned to connect the pipe 17 to the pipe 19, increasing liquid level in the float chamber 16 closes the valve 10 either partially or completely, thus reducing or stopping the flow of power fluid through the pipe 8, resulting in reduction of the amount of gas pumped by the ejector 8. The type of action may be either throttling or snap acting.

A decrease in liquid level in the accumulator chamber 13 results in a decrease of liquid level in the float chamber 16. The action is opposite to that of increasing liquid level. When the three way valve 18 is positioned to connect the pipe 17 to the pipe 19, increasing liquid level in the float chamber 16 closes the valve 15, either partially or completely, thus decreasing the suction pressure on the ejector 8, and reducing the amount of gas pumped.

The type of action may be throttling or snap acting as best suits the rest'of the installation. Decreasing liquid level in the float chamber 16 leads to results opposite to those of increasing liquid level.

An opening 26 (Figs. 2 to 4) is provided through the upper surface of the movable suction pipe 5. A plate 30 is provided inside of the suction pipe 5 at the opening 26 in a manner which leaves a slot 31 open. The plate 30, the opening 26, and the slot 31 may be easily and simultaneously formed by cutting through the wall of the suction pipe 5 with an oxy-acetylene torch to cut out three sides of arectangle, then bending the rectangle inwardly of the pipe 5 along its fourth side, and partially or completely welding the longitudinal cuts to, close them on the two sides adjacent its fourth side, using plates 36, if necessary. When the longitudinal cuts are onlypartially closed by welding as shown, part of the plate is cut off .to enlarge, the slot 31.

A plate 33is placed over the opening 26, and is either welded or bolted in place. A, short pipe 27 is connected to a hole 34 in the p'late 33. A number of bars 36 .are welded in the slot and form a strainer.

An ejector 50 (Fig. l) ispr'ovided, with its suction opening connected to the hole 34 through the short pipe 27. Power fluid is furnished, to the ejector 50 through a, pipe 51 which is controlled by a valve 52. The ejector 5t). discharges through a check valve 53. One or more portions of the pipe 51 are flexible or swing jointed in order to accommodate the rotation of ,the movable suction pipeuS about the ball joint 6 and/or the movement of the ball joint 7. v

In, operation, the ejector 50 operates under a higher suction pressure than the ejector 8, and thereforeremoves gases from the. suction system more economically than the ejector 8. Dredged liquidmoving up the movable suction pipe 5, if no gases have collected, is deflected by the plate 30, resulting in an increase in pressure on the lower face of the plate 30 and a decrease in pressure in the slot 31. Decreased pressure in the slot 31 will tend to reduce the movement of liquid through the slot 31 and the opening26 and the hole 34 into the pipe 27, in case a tendency exists for such movement. When collected gas arrives at the plate 30, it depresses the dredged liquid away from the plate 30, removing the increased pressure on the plate 30 and also the decreased pressure in the slot 31. It is obvious that gas passes through the slot 31 more easily than liquid passes.

An opening 26' (Figs. 1, 5 and 6) is provided through.

the upper surface ,of the movable suction pipe 5 The opening 26 is connected through a. pipe 27 having one or more flexible portions 28, to a check valve 29 near the outer end of the pipe 27. The check valve 29 permi ts flow out of the pipe 27, but not in the reverse direction. The check valve 129 may be located below, at, or above, the surface 45 of the water in which the dredge is operating. An alternate surface 45' is indicated. Two or more of the openings 26 may be placed in the suction pipe 5, each connected to a separate pipe 27', flexible portion of pipe 28, and check valve 29, if desired. The

opening 26 is 50 located along the length of the movable suction pipe 5 that the pressure inside of the suctionpipe 5 near the opening 26' usually exceeds the external pressure on the checkvalve 29while dredging gaseous material. A hinged plate 30 is provided inside of the suction pipe5 at the opening 26 in a manner which leaves a slot 31 open. The plate 30 is hinged at a hinge 32 which has a stop to limit the downward movement of the plate 30'. The plate 30 may alternatively be madeof rubber or other flexible material, in which case the hinge 32 is unnecessary, but will exist in eflcct due to the flexibility of the plate 30. A plate 33. with an opening 34 is bolted. over the opening26'. One or more holes 35 are provided in the plate 33 to allow water to enter.

A flexible flap 39 is placed over the hole 34 as a check valve. This flap is held in place by a strip 40 and cap screws 41. A box is provided, of which the plate 33 forms, the bottom, with four sides42 and a cover 43.

Connection is made to the pipe 27' through a hole 44..-

The cover 43 is bolted to the sides 42. This arrangement is principally for use when morethan one opening 26' is connected to one pipe 27. When pressure conditions are such as to tend to otherwise move gases from the pipe 27 through one of the openings 26f into the interior of'themovable suction pipe5,the flap 39 associatedwith that opening 26' closes, preventing such movement. Thus the lowest opening 26 will continue to function as an escape route for gases, even though the remaining openings 26' cannot so function due to lack of suflicient pressure within the movablesuction pipe. 5 in their vicinity.

In operation, gases which have collected along the upper portion of the inside of the movable suction pipe 5 pass through the opening 26, the opening 34, the pipe 27, and the check valve 29, and escape to atmosphere. Should the pressure near one of these openings 26 be momentarily less than that outside of the check valve 29, the check valve 29 Will prevent air from being drawn into the pipe 27 and thence into the movable suction pipe 5. Water entering through the holes 35 continually washes the slot 31. .Shouldthe pressure within the movable suction pipe 5 in the, vicinity of the slot 31 be high enough to force dredged liquid through the slot 31, water entering through the holes 35 will fill the space between the plate 30 and the plate 33 and may enter the pipe 27, instead of the mud that might so do in the absence of the holes 35. Thus, when gases later arrive at the slot;3,1' they canmore easily be discharged through the water than they could through mud.

If no gaseshave collected, dredged liquid moving up the movable suction pipe 5 forces the hinged plate 30 upward, tending to close the slot 31. Partial closure of the slot 31', and decreased pressure in the slot 31' will both tend to reduce the movement of liquid from inside of the suction pipe 5 through the slot 31. in case a tendency exists for such movement.

A hingestop 49 (Figs. 1, 7 and 8) is provided to limit the downward motion of the plate 30'. A plate 33" is bolted to the suction pipe 5. The plate 33 is pierced by a hole 34 to which is connected the pipe 27. One or more holes 35' are provided for allowing water to enter.

An opening 26 as shown in Figs. 2 to 4, if properly located on the suctionpipe 5, maybe connected to the pipe 27 instead of the pipe 27 and the ejector 50. An opening 26 with the ejector 50 has an advantage over an opening such as the opening 26"with its pipe 27', in that the former may be placed at a point along the length of the movable suction pipe 5 or the fixed suction pipe 3 where the internal pressure is less than atmospheric pressure, which means it can be placed at a point higher up the movable suction pipe 5, where there is usually more gas collected and available for removal.

In the modification shown in Fig. 9, a hinged plate 30 is provided inside of the suction pipe 5. A number of plates of peculiar shape are Welded to the upper surface of the plate 30". The purpose of the plates 55 is to limit the downward motion of the plate 30" about the pivot point 32, to act as a strainer to deter debris frommoving out of the movable suction pipe 5 through the slot 31', and to provide a slotted hole 58. A pivot point 61 is provided. An arm is rigidly fastened to a float 59 and pivoted about the pivot point 61. The float 59 is faced with rubber to seal the end of a pipe 27" when in the proper position. An arm 57 is pivoted on the float 59 and its other end is pivoted in the slotted hole 58. A box is provided comprising four sides 63 and a top 64, through the sides and top of which one or more openings 35" are provided for water. The top 64 is bolted to the sides 63. The pipe 27" is similar to the pipe 27 and connects the box to a check valve near the surface of the water.

In operation, gas normally passes from inside the movable suction pipe 5,through the slot 31' and into the pipe 27" whence it escapes. When gas is'no longer present, liquid pressure forces the plate 30" upward about the pivot point 32, acting through the arm 57 to move the rubber facing on the float 59 over the end of the pipe 27" and thus seal it. Also, water entering through the openings 35" partially fills the space between the plate 30" and the top 64, causing the float 59 to seal the pipe 27", just as the action of the plate 30" does. When gas later arrives inside the movable suction pipe 5 in the vicinity of the plate 30", the upward force on the plate 30" is removed, and it drops, opening the slot 31'. The water between the plate 30 and the top 64 flows through the slot 31' into the movable suction pipe 5, or is blown out through the pipe 27". When the plate 30" is as far down as the plates 55 will allow, the relations of the slotted hole 58 and the arm 57 are such that the rubber facing of the float 59 is pulled away from the end of the pipe 27".

This same arrangement, if the parts are properly proportioned, will operate satisfactorily without the pivot point 32, and with the plate 30" rigid. With this arrangement, the longitudinal openings between the plate 30" and the wall of the movable suction 5 are welded partially or completely closed, and the slotted hole 58, and the arm 57 are not used. The plates 55 are welded at both ends, forming a solidly fastened strainer.

In operation, flotation of the float 59 on the water entering through the openings 35" will result in sealing of the end of the pipe 27" when a tendency exists for dredged material to move out of the movable suction pipe 5 through the slot 31.

An air pipe 69 (Fig. 1) is provided for compressed air, including one or more flexible portions 72 to accommodate motion in the non-rigid portions, if any, of the movable suction pipe 5. Compressed air entering the air pipe 69 is controlled by a valve 73. A curved portion 70 is provided at the lower end of the air pipe 69 and is attached to the surface of the suction pipe 5. The curved portion 70 is perforated with a number of small holes 70 which match similar holes through the wall of the movable suction pipe 5. An air lift is thus introduced into the movable suction pipe 5, promoting more rapid movement of the dredged material therein. Air entering the movable suction pipe 5 through the holes 70' decreases the density of the dredged material, and later is removed by other means described herein. Several groups of holes 70' may be located at various points along the length of the movable suction pipe 5 fed by a common air pipe 69, or each group may be fed by a separate air pipe 69 with separate control valve 73, or gases may be fed to a group of holes 70' from any of the openings shown in Figs. 2 to 9 which is sufl'iciently farther down the suction pipe 5 to have the proper pressure relationship.

A group of holes 54 (Fig. 1) is provided extending through the wall of the movable suction pipe 5 in order to permit entrance of water into this pipe. In order that water so entering will disturb the stream of liquid as little as possible, these holes are tilted as much as practicable, so that the water entering through them is moving nearly parallel to the stream of dredged liquid. The holes 54 are spaced around the periphery of the movable suction pipe 5, and tilted, so as to promote the formation of a layer of relatively clean water immediately on the inner surface of this pipe, thereby resulting in considerably lowered viscosity of liquid in this layer, leading to less friction loss than if the layer next to the pipe were mud. Since gas often occupies the upper portion of the interior of the movable suction pipe 5, the hole or holes in the upper portion of this pipe may be omitted. Each hole 54 may be slightly tapered, in order that it may be plugged if desired with a tapered plug, thus providing means for adjusting the number of holes in use. Additional groups of holes 54 may be placed at any location along the length of the movable suction pipe 5 which is below the surface 45 (45) of the water.

What I claim is:

1. A hydraulic dredge comprising a gas accumulator chamber, a suction pipe in communication with said chamber, a centrifugal pump in communication with said suction pipe, a float chamber external to said accumulator chamber, upper and lower conduits connecting said float chamber to said accumulator chamber, a float in said float chamber, said float being responsive to changes in the liquid level in said accumulator chamber, means for prohibiting the flow of gases and other dredged material through the lower one of said conduits and for supplying auxiliary water for operation of said float, said means comprising a check valve permitting flow to said accumulator chamber and a connection for continuously introducing auxiliary water into the lower one of said conduits on the side of said valve toward said float chamber.

2. A hydraulic dredge comprising a suction pipe, a centrifugal pump in communication with said suction pipe, said suction pipe having an opening through the upper wall thereof at a position Where the pressure inside said suction pipe exceeds atmospheric pressure when dredging gaseous material, a plate partially covering said opening and extending into said pipe and a connection from said opening to the atmosphere for conveying gas from said suction pipe to the atmosphere when said dredge is operating said connection sloping continuously downward from its highest point.

3. In a hydraulic dredge, a check valve, a suction pipe, a centrifugal pump in communication with said suction pipe, said suction pipe having an outlet through the upper wall thereof below the surface of the water in which the dredge is operating and a conduit connecting said outlet through said check valve to a point of lower pressure than usually exists in said outlet, said check valve permitting flow from said outlet toward said point of lower pressure, and said conduit sloping continuously downward from its highest point, said conduit being principally filled with gas when said dredge is dredging gaseous materials.

4. A hydraulic dredge comprising a movable suction pipe, a centrifugal pump in communication with said suction pipe, means to continuously introduce gas under pressure into said pipe below the centerline of said pump while said pump is dredging, and means to continuously remove said gas directly from said pipe at an elevation higher than its point of introduction and before reaching said pump.

References Cited in the file of this patent UNITED STATES PATENTS 491,843 Kauser Feb. 14, 1893 521,883 Holland June 26, 1894 528,977 Pike Nov. 13, 1894 906,234 Jackson Dec. 8, 1903 790,702 Nash May 23, 1905 909,543 Carlesimo Ian. 12, 1909 910,277 Eliel Jan. 19, 1909 918,302 Eliel Apr. 13, 1909 1,229,772 Miller et al. June 12, 1917 1,327,651 Beaver Ian. 13, 1920 1,372,139 Hogue Mar. 22, 1921 1,382,665 Myers June 28, 1921 1,455,211 Kelly May 15, 1923 1,508,521 Kreuser Sept. 16, 1924 1,789,528 Lewis Jan. 20, 1931 1,971,441 Broadhurst Aug. 28, 1934 2,033,980 Durdin Mar. 17, 1936 2,057,570 Haentjens Oct. 13, 1936 2,096,595 Sanford Oct. 19, 1937 2,158,785 Hall May 16, 1939 2,356,970 Brockett Aug. 29, 1944 FOREIGN PATENTS 656,391 France Ian. 2, 1929 793,407 France Nov. 16, 1935 364,865 Germany Dec. 6, 1922 6,421 Great Britain Apr. 15, 1889 150,015 Great Britain Aug. 23, 1920 323,407 Great Britain Ian. 2, 1930 

